Q690C低碳粒贝钢多层MAG焊接头组织与性能

为提高效率、获得理想断裂位置并改善热影响区韧性,对控扎控冷工艺生产的8 mm厚Q690C低碳粒贝钢,选用等强度匹配的焊丝,采用无预热、低热输入(10 kJ/cm以下)三层全自动MAG工艺施焊.结果表明,无裂纹与成形缺陷;拉、弯与冲击性能均合格.焊缝为针状铁素体,韧性优异;仅在较窄的部分相变区(单道约0.2~0.4 mm)因回火而出现软化,但未对抗拉性能形成危害;因热输入低,拉伸断裂位置距焊缝更远;虽然熔合区与粗晶区为粗大平行上贝板条束+M-A组元,出现了硬化,但低热输入的低过热效果与两次后续焊道对贝氏体基体的明显回火作用改善了熔合区在0℃的冲击韧性.     

热输入对3Cr耐候钢MAG焊缝金属组织和性能的影响

采用三种热输入进行3Cr耐候钢MAG焊,借助金相显微镜、扫描电子显微镜及透射电子显微镜分析了热输入对焊缝金属组织和性能的影响.结果表明,三种热输入焊缝金属组织主要由板条贝氏体、粒状贝氏体和M-A组元组成.随着焊接热输入的增加,焊缝组织中粒状贝氏体含量增加;M-A组元含量增加且尺寸增大.随着热输入的增加,焊缝金属冲击韧性降低.组织粗化、M-A组元含量增加尺寸增大是导致其韧性降低的主要原因.接头不同区域耐蚀性能相当,腐蚀产物主要由α-FeOOH组成.热输入为8~12 kJ,采用所选焊丝焊接高强耐候钢能够获得强韧性、耐蚀性匹配良好的焊接接头.热输入为8 kJ,接头综合性能最佳.     

700MPa级低合金高强钢低匹配焊接接头组织和性能研究

按照低匹配设计原则,采用熔化极气体保护焊对屈服强度为700 MPa级的低合金高强钢进行了焊接。采用光学显微镜、扫描电镜和力学性能试验研究了焊接接头的组织和性能。结果表明,焊缝区组织主要为针状铁素体和少量先共析铁素体,粗晶热影响区组织为上贝氏体;焊缝区显微硬度明显低于母材,焊缝区-40℃时的冲击韧度(AKV)为58 J,抗拉强度达到了母材抗拉强度的92.4%,焊接接头的综合力学性能良好。     

G115钢CMT + P焊接工艺及组织和性能

基于冷金属过渡加脉冲(CMT + P)的焊接方法,研究了新型回火马氏体耐热钢G115的焊接性以及焊接接头组织和性能. 结果表明,焊接接头经热处理后为回火马氏体组织,焊缝晶粒呈现出等轴晶和柱状晶两种不同的形貌,而焊接热影响区和母材晶粒均为等轴晶. 与焊条电弧焊(SMAW)相比,CMT + P焊接方法有效降低了热输入,大幅度减小了热影响区宽度,提高了焊接接头的拉伸性能和热影响区冲击韧性,焊接接头焊缝冲击韧性略有降低. 焊接接头的室温和高温拉伸断裂机理均为韧性断裂,室温拉伸断口的韧窝内存在一定量的析出相.     

母材熔合作用对EQ51海工钢焊缝组织及韧性的影响

文中采用示波冲击,EBSD,SEM研究了母材元素含量、坡口形式、焊接热输入对海洋工程用钢EQ51焊缝组织转变、低温冲击韧性及焊接接头软化程度的影响规律.结果表明,C,Mn元素含量对焊缝组织类型、取向趋势起关键作用,含量由0.1%,1.5%分别调整为0.06%,1.3%,可保证焊缝组织由板条贝氏体转化为针状铁素体,组织止裂能力显著提高,冲击吸收功大于100 J;适当提高焊接热输入一定程度上可降低淬硬元素对韧性的不利影响;Ni,Mo元素含量对焊缝组织、韧性影响不大,主要决定焊接接头软化程度,Ni,Mo元素总添加量由0.7%下降到0.4%,软化区宽度由1 mm提高到2 mm,焊接接头抗拉强度由789 MPa降低到650 MPa.     

新型9Cr-1Mo钢搅拌摩擦焊接头组织及性能

采用钨铼合金搅拌工具对新型9Cr-1Mo钢进行搅拌摩擦焊工艺试验,探讨焊缝成形、组织及性能变化规律. 结果表明,在300和400 r/min的转速,50 mm/min的焊接速度下可获得无缺陷接头;焊缝主要由搅拌区和热力影响区组成,具有明显的马氏体淬硬组织特征;高温热影响区为淬硬马氏体和回火马氏体混合组织,低温热影响区为过回火马氏体组织. 焊缝区具有晶粒细化特征,其晶粒尺寸约为母材69.2%. 焊缝区产生明显硬化,最高硬度约为母材硬度值的2.0倍. 焊接接头抗拉强度达到母材98%以上,搅拌区和热影响区冲击吸收能量分别达到母材的77.8%和87.4%,表明搅拌摩擦焊接头仍具有较好强韧匹配.     

厚板AZ31镁合金搅拌摩擦焊焊接接头的组织与性能

对10mm厚板A231镁合金成功进行了搅拌摩擦焊接,获得成形良好、表面光滑、无裂纹、无气孔的焊接接头.研究该搅拌摩擦焊接头不同区域的显微组织特征,并通过拉伸、冲击和硬度试验分析了焊接接头的力学性能.结果表明,焊缝中心区是均匀细小的等轴晶粒,热力影响区晶粒大小不均匀,存在较明显的塑性流变带结构;焊接接头的抗拉强度达到母材的80%以上,焊接接头的冲击韧性比母材高,焊接接头的显微硬度比母材稍有降低,焊接接头具有较好的力学性能,说明搅拌摩擦焊是焊接厚板镁合金的一种有效方法.     

Fracture toughness of structural aluminium alloy thick plate joints by friction stir welding

Abstract

The fracture toughness in a friction stir welded joint of thick plates of structural aluminium alloy type A5083-O is investigated. A joint between two 25 mm thick plates is fabricated by one sided, one pass friction stir welding. The Charpy impact energy and critical crack tip opening displacement (CTOD) in the friction stir weld are much higher than those in the base metal or heat affected zone, whereas mechanical properties such as stress–strain curve and Vickers hardness are not conspicuously different. The effects of the microstructure on crack initiation and propagation are studied in order to clarify the difference in fracture toughness between the stir zone and base metal. The analyses of the fracture resistance curves and the diameters of dimples in the fracture surface after both tensile and bending tests show that the fine grained microstructure in the stir zone helps to increase ductile crack initiation and propagation resistance. It is found that the high fracture toughness value in the stir zone is affected by the fine grained microstructure in friction stir welds.     

钛合金TIG焊接头晶粒尺寸非线性梯度特征

以显微组织与晶粒尺寸统计分析为基础,研究了TC4钛合金不同TIG焊工艺的焊接接头显微组织及其晶粒尺寸变化,引入了晶粒梯度特征值概念,以表征钛合金焊接接头显微组织的非均匀性.结果表明,TC4钛合金TIG焊接头显微组织的晶粒尺寸从焊缝中心经热影响区至母材呈现非线性变化,晶粒尺寸变化率(晶粒梯度)在柱状晶区(CZ)和粗晶区(CGZ)交界处出现最大值,称之为晶粒梯度特征值;随着TIG焊热输入增大,晶粒梯度特征值逐渐减小,但相对位置不发生改变.晶粒尺寸梯度特征值能够反映钛合金焊接接头组织的不均匀性,这对于探索钛合金焊接接头的服役性能具有重要的意义.     

提高P91耐热钢焊接接头冲击韧度的研究

探讨了影响P91耐热钢焊接接头冲击韧度的工艺因素,对P91钢的常规焊接工艺进行调整,并模拟该工艺进行焊接试验。最后通过拉伸、弯曲、冲击试验、断口扫描和金相观察检验接头组织及性能。结果表明,在模拟焊接工艺下,P91耐热钢可以获得良好的焊接接头。焊缝拉伸强度高于母材;焊缝侧向弯曲试验外弧面未发现开裂;焊接接头的显微组织为回火板条马氏体,未出现非正常组织,焊缝晶粒明显细化;接头冲击韧度得到了大幅度提高。     

超细晶Q460钢CO2气体保护焊焊接接头组织与性能

采用CO2气体保护焊选择ER55-G焊丝焊接了超细晶Q460钢,研究了焊接接头显微组织、断口形貌以及力学性能。结果表明,焊缝主要由铁素体和少量珠光体构成,焊缝中大量针状铁素体的生成有利于提高焊缝金属的强度和韧性。焊接接头热影响区粗晶区为贝氏体组织,相变重结晶区和不完全重结晶区未出现软化现象。焊缝金属同热影响区冲击断口均为韧窝状韧性断裂,由于超细晶Q460钢材质的高度纯净化以及焊接过程中较小线能量的选择,焊接接头热影响区表现出优异的冲击韧性。     

X90管线钢管埋弧焊缝组织与性能分析

X90管线钢管是目前正在研究开发的一种新型高强度管线钢管. 随着管材强度的提高,焊缝的组织与性能成为研究与控制的关键. 文中对焊缝、热影响区(HAZ)和母材微观组织、晶粒取向、大/小角度晶界占比及冲击断口形貌等进行了分析研究. 结果表明,焊缝试样近断口区组织为针状铁素体(AF)+准多边形铁素体(QPF),M-A组元呈楔形、块状和条带状,分布于相界处,尺寸较大,长1.8 μm,宽0.5 μm,组织有效平均晶粒尺寸为3.12 μm,大角度晶界比例为67.15%;而HAZ试样近断口区组织为粒状贝氏体(GB)+多形态M-A组元,晶粒粗大,M-A组元多以条带状、楔形分布于晶界和晶内,组织有效平均晶粒尺寸为4.52 μm,大角度晶界比例为85.95%. 母材试样近断口区组织是以细小AF+QPF+板条贝氏体(LB)+少量M-A组元为主的多相匹配的复相组织,M-A组元尺寸细小,组织有效平均晶粒尺寸为2.1 μm,大角度晶界比例为93.75%.密集分布的大尺寸M-A组元和大角晶界占比较小是导致焊缝冲击韧性低于母材的重要原因.     

不同热处理状态AMS6308钢惯性摩擦焊接头组织及力学性能

在HWI-IFW-130型轴/径向多功能惯性摩擦焊机上,成功实现热轧态与热轧态AMS6308钢、淬火+回火态与淬火+回火态AMS6308钢惯性摩擦焊接. 对两种不同热处理状态的焊接接头进行检测分析. 结果表明,母材为热轧态的焊接接头,焊缝区为马氏体组织,热力影响区和热影响区为马氏体+贝氏体组织;母材为淬火+回火态的焊接接头,焊缝区为马氏体组织,热力影响区和热影响区为马氏体回火组织. 以焊缝为中心,显微维氏硬度呈对称分布,焊缝区显微维氏硬度最高;两种不同热处理状态母材获得的焊接接头,拉伸均断于母材.     

Incoloy 825镍基高温合金电子束焊工艺及接头组织与力学性能分析

采用电子束焊,对空冷器管箱Incoloy 825镍基高温合金进行对接焊试验. 通过对焊接接头的组织观察,并结合拉伸力学性能以及接头的冲击韧性等试验,分析镍基高温合金电子束焊接头的组织和力学性能. 结果表明, 采用电子束焊焊接镍基高温合金可以得到良好的焊接接头,焊缝区组织由大片等轴晶和少量柱状晶组成;焊缝区没有出现明显的元素烧损现象;焊缝、热影响区硬度达到母材硬度值;焊缝接头抗拉强度达到600 MPa,接近母材抗拉强度,接头断裂形式为韧性断裂;焊缝和热影响区的冲击吸收能量高于母材区,其中焊缝区的冲击吸收能量达到了262 J,冲击断口形貌为韧窝状.     

Influence of Welding Thermal Cycle on Microstructure and Properties in Heat-affected Zone of X80 Pipeline Steel

Single welding thermal–cycles with different input linear energies (ILE)(15, 20, 30, 40, 50 kJ/cm) and peak temperatures (PT) (900, 1050, 1200, 1300, 1350 ℃) were simulated by MMS-300 to study the correlation of toughness and microstructure in heat-affected zone (HAZ) of a X80 pipeline. The evolution characteristics of microstructure were investigated by OM, SEM and EBSD. The results show that numerous polygonal ferrites and grain boundary ferrites appear, and the sizes apparently decrease as the heat input decreases. Heat input in single welding should be less than 35 kJ/cm to ensure well Charpy impact toughness. The toughness of course grain zone is the lowest when welding heating temperature is 1350 ℃ and it is the weakness part in welded zone. The uniformity of prior austenite grain is worsened as increasing the heat input. Moreover, the characteristics of M-A constituents and high angle grain boundaries (HAGB) are influenced by heat input and PT. In the case of low heat input and PT, higher density of HAGBs, dispersed and fine M-A constituents were observed. Otherwise, with high heat input (≥40 kJ/cm), the effective grain size is almost the diameter of prior austenite grain, and it will decrease the density of HAGB, moreover, coarse M-A constituents which are prone to crack initiation will be generated, thus, the impact toughness of the coarse grain zone will be worsened obviously in welding HAZ.     

低活化铁素体/马氏体钢厚板光纤激光焊接接头组织及力学性能分析

针对核聚变反应堆试验包层模块(TBM)中使用的CLF-1低活化铁素体/马氏体钢进行焊接试验,采用15 kW光纤激光,实现了17.5 mm厚CLF-1钢的穿透焊接,得到了正反表面成形良好、无明显缺陷的焊接接头,并对接头显微组织及力学性能进行了分析研究. 结果表明,焊缝区主要为粗大的板条马氏体;熔合线附近热影响区为细小的板条马氏体和少量贝氏体;不完全淬火区为经焊接热循环作用下二次回火的回火索氏体及马氏体双相组织;接头室温及550 ℃高温抗拉强度较高,均断裂于母材;焊缝显微硬度高于母材,且热影响区无明显软化;接头冲击韧性良好. 接头综合力学性能良好.     

Investigation of Corrosion Behavior of Welded Joint of X70 Pipeline Steel for Deep SeaEI北大核心CSCD

X70 pipeline steel with thick specifications (40.5 mm) for 3500 m deep sea reached the international advanced level in the wall thickness and service depth. Due to the high heat input during the welding process, the corrosion resistance of inside welding and outside welding would vary depending on the microstructure differences. The corrosion resistance of the welded joints of X70 pipeline for deep sea was studied by the immersion test, the weight loss test, the electrochemical test in this work. The components of the passive film were analyzed by XRD and the microstructure was observed by SEM. The results show that the corrosion resistance of the weld metal is the best. The corrosion resistance of the heat affected zone follows. The corrosion resistance of the base metal is the worst. And for the same area, the corrosion resistance of the inside welding is better than that of the outside welding. The formation of dense Fe3O4 passivation film can effectively slow down the progress of the reaction, and the corrosion products of Fe2O3, FeOOH and Fe(OH)(3) which are loose in the outer layer, have no protective effect on the matrix. The microstructure of the weld metal with the best corrosion resistance is mostly the intragranular nucleation ferrite and martensite-austenite (M-A) constituent is fine and uniform. The microstructure gradient of the heat affected zone is the largest, the M-A constituent is coarse and the corrosion resistance is inferior to the weld metal. The base metal consists of ferrite and bainite, the bainite is island-like distribution and the corrosion resistance is the worst. Microstructure of the inside welding is more refined, owing to the influence of outside welding thermal cycle, and the volume fraction of M-A constituent in inside welding is higher than that of the outside welding, so the corrosion resistance is better than that of the outside welding.     

超纯铁素体Cr30Mo2钢焊接接头的组织和力学性能

利用自制的焊接工作台,在ＴＩＧ焊基础上,对Ｃｅ３０Ｍｏ２超纯铁素体不锈施焊。焊接中对焊缝和热影响区附加拖罩和背;衬的Ａｒ气延续保护。对焊接接头质量进行宏观坶检验;借助金相显微镜、扫描电镜（ＳＥＭ）、透射电镜（ＴＥＭ）分析焊缝组织特征一冲击断口形貌;按国家标准测试焊接接头的力学性能。华发头上未发现任何焊接缺陷,焊接缝质量良好;其强度、延性和韧性均达到母材水平,特别是在焊缝和热影响区未出现脆化现象,冲     

热输入对800MPa级超厚板窄间隙焊缝金属组织和性能的影响

采用三种热输入进行超厚板窄间隙熔化极气体保护焊,借助金相显微镜、扫描电子显微镜及附带EDS系统和透射电子显微镜研究了热输入对焊缝金属组织和性能的影响.结果表明,三种热输入焊缝金属组织主要由板条马氏体、无碳化物贝氏体、M-A组元和残余奥氏体组成.随着焊接热输入的增加,焊缝组织中马氏体含量减少;也使无碳化物贝氏体形核率降低,造成无碳化物贝氏体粗化.并且当贝氏体相变时热输入的增加使碳原子扩散距离变远,促使残余奥氏体形状由膜状向块状转变.另外随着热输入的增加,焊缝金属强度下降,而冲击韧性对热输入不敏感.     

热输入对BWELDY960Q钢焊接接头组织性能的影响

采用MAG焊方法焊接低合金高强度钢BWELDY960Q,在不同焊接工艺参数下获得焊接接头,研究焊接热输入对焊接接头组织性能的影响. 结果表明,随着焊接热输入的提高,焊缝中针状铁素体的体积分数呈现先增加后减少的趋势,当焊接热输入为12.32 kJ/cm时,焊缝中获得的针状铁素体所占的比例达到最大值. 针状铁素体数量的增加,提高了焊缝和熔合区的冲击吸收功、焊接接头的抗拉强度、断后伸长率和断面收缩率. 焊缝冲击断口呈韧窝花样,等轴韧窝与抛物线韧窝交替分布. 熔合区冲击断口呈解理特征,解理台阶层次明显,并存在较多的撕裂棱.